It seems like this elides the difference between the goals of humanities education and the actual practice and outcomes of humanities education. I honestly don't know if humanities education confers the ability to "read closely, think clearly and critically, and synthesize information" at a rate that's so much higher than STEM education that it makes sense to divert tens of thousands of dollars to a humanities major instead of a STEM one.
Just as some naive first cut at answering this, I looked up GRE scores by intended graduate major [1]. "Physical sciences" (including math) majors average a 151 Verbal and "Humanities and Arts" average a...156, which seems pretty close, and even closer if you squint to try and account for the fact that the physical sciences skews English-as-a-second-language more than the humanities?
Of course, the GRE isn't a perfect proxy for the ability to "read closely, think clearly and critically, and synthesize information", but...graduate schools seem ok with it?